NAME
Lexical::Alias - makes a lexical an alias for another variable
SYNOPSIS
use 5.008;
use Lexical::Alias;
my ($src, $dst);
alias $src, $dst;
my (@src, @dst);
alias @src, @dst;
my (%src, %dst);
alias %src, %dst;
# modifying $src/@src/%src
# modifies $dst/@dst/%dst,
# and vice-versa
# or, if supporting Perls prior to v5.8:
use Lexical::Alias qw( alias_r alias_s alias_a alias_h );
my ($src, $dst);
alias_s $src, $dst;
my (@src, @dst);
alias_a @src, @dst;
my (%src, %dst);
alias_h %src, %dst;
alias_r \$src, \$dst;
alias_r \@src, \@dst;
alias_r \%src, \%dst;
# if you prefer the alias come first...
$Lexical::Alias::SWAP = 1;
alias $dst, $src; # $dst is an alias for $src
DESCRIPTION
This module allows you to alias a lexical (declared with "my") variable
to another variable (package or lexical). You will receive a fatal error
if you try aliasing a scalar to something that is not a scalar (etc.).
Parameter Swaping (new!)
Version 0.04 introduced the $Lexical::Alias::SWAP variable. When it is
true, the arguments to the aliasing functions are expected in reverse
order; that is, the alias comes *first*, and the source variable second.
(Thanks to Jenda from perlmonks.org for requesting this.)
Exported Functions
* "alias(src, dst)"
Makes *dst* (which must be lexical) an alias to *src* (which can be
either lexical or a package variable). *src* and *dst* must be the
same data type (scalar and scalar, array and array, hash and hash).
This is only available in Perl v5.8 and later, where it is exported
automatically.
* "alias_s($src, $dst)"
Makes *dst* (which must be lexical) an alias to *src* (which can be
either lexical or a package variable). This is not exported by
default.
* "alias_a(@src, @dst)"
Makes *dst* (which must be lexical) an alias to *src* (which can be
either lexical or a package variable). This is not exported by
default.
* "alias_h(%src, %dst)"
Makes *dst* (which must be lexical) an alias to *src* (which can be
either lexical or a package variable). This is not exported by
default.
* "alias_r(\src, \dst)"
Makes *dst* (which must be lexical) an alias to *src* (which can be
either lexical or a package variable). *src* and *dst* must be the
same data type (scalar and scalar, array and array, hash and hash).
This is not exported by default.
Caveats
If you alias one lexical to another lexical, then making another alias
to either lexical makes *all three lexicals* point to the same data.
use Lexical::Alias;
my ($x, $y, $z);
alias $x => $y; # $y is an alias for $x
alias $z => $y; # $y (and thus $x) is an alias for $z
$z = 10;
print $x; # 10
This is not a bug.
However, there *does* appear to be a bug in Perl 5.8.0 (which has been
fixed in the development version 5.9.0); when these functions are used
in a subroutine, they appear to not work fully:
my $orig = 1;
my $alias = 99;
alias $orig => $alias;
print "$orig = $alias\n";
sub foo {
my $orig = 1;
my $alias = 99;
alias $orig => $alias;
print "foo(): $orig = $alias\n";
}
foo();
The expected output is "1 = 1" and "foo(): 1 = 1". It is not so. The
second output is "foo(): 1 = 99". Jenda pointed this out to me, and I do
not know where in the source the bug is, but it will be fixed for the
next release of Perl (5.8.1).
AUTHOR
Jeff "japhy" Pinyan, japhy@pobox.com
Thanks to Tye McQueen for a bug fix -- this module should work from
5.005 on.
http://www.pobox.com/~japhy/
SEE ALSO
Devel::LexAlias, by Richard Clamp, from which I got (and modified) the
code necessary for this module. I've wanted this feature for some time,
and Richard opened the door with this module.
Variable::Alias, by Brent Dax, which is a tie() interface to aliasing
all sorts of variables.